The invention relates to a threaded bolt.
A threaded bolt is known from U.S. Pat. No. 4,952,110. This threaded bolt is provided with an eccentric tip with a smooth portion and a threaded portion, located opposite each other. The threaded portion of the eccentric tip is located on the surfaces that are substantially aligned with the threaded surfaces of the shank of the threaded bolt. The smooth surfaces are located at the areas of the tip that are radially inwardly shifted with respect to the threaded surfaces of the shank.
In the known threaded bolt, the eccentric arrangement of the tip also provides a means for axial alignment of the central axis of the threaded bolt and the central axis of the nut or tapped hole. The threaded side of the tip helps to prevent an inclined position (xe2x80x9ccross-threadsxe2x80x9d) of the threaded bolt.
Cross-threading occurs when a threaded bolt, especially in the automobile industry, does not precisely, or with a deviation of more than 5xc2x0 with respect to the perpendicular direction of insertion, fit in a nut or tapped hole. Such a form of cross-threading is also called angular deviation.
From U.S. Pat. No. 4.981.406 a threaded bolt is known with a threaded shank and a tip that may be threaded on one side and may be smooth on the other side, possibly with inwardly shifted areas, and the central axis of which is at an angle with or parallel, yet staggered, to the central axis of the shank.
From the European patent application 0.475.712 a threaded bolt is known with a threaded shank and with a tip, the surface of which, on one side, forms a continuation of the thread of the shank and, on the other side, is smooth and is tapered in distal direction.
All the cited, known threaded bolts have the disadvantage that, although they provide a certain degree of alignment, the threaded portion on the tip results in a destruction of the thread of the nut or tapped hole when the insertion position of the threaded bolt is too oblique. It has to be kept in mind here that, especially in the automobile industry, robots are used to screw the threaded bolts in the appropriate holes with a predetermined turning moment. This means that, independent of the situation the threaded bolt that is to be screwed in encounters, the threaded bolt is rotated in until the required tightening moment, which, if the thread has an incorrect position with respect to the screw hole, may result in an unacceptable degree of deformation of either of the threads when they interact. The connection in question will then not be as it should be, as a result of which, after this has been ascertained, the connection will either have to be repaired, causing loss of time, or a certain degree of danger will have been created for the period during which the end product, particularly a motor-car, is used.
Other known threaded bolts have a tip that is provided with a circumferential thread that forms a continuation of the thread of the shank, yet wherein the tip is centrically tapered. Such threaded bolts are not given preference because a tip like that is difficult to manufacture, while, in addition, the effect with respect to the realization of the alignment of the central axis of nut or tapped hole and threaded bolt is very limited.
Another known threaded bolt has a threaded shank that is provided with a truncated conically shaped, centric, smooth head, in which a circular cylinder portion is provided between the smooth head and the shank, which circular cylinder portion is also smooth and has a diameter that is smaller than the inner diameter of the thread on the shank. The aligning function of this bolt, too, leaves much to be desired.
Another, similar threaded bolt has a truncated conically shaped, centric, smooth head with a convex generatrix and, in proximal direction, connecting smooth, circular cylinder-shaped surfaces, the diameter of which substantially corresponds to the inner diameter of the threaded shank.
In the automotive industry, in particular, it is becoming more and more difficult to attune the parts that have to be assembled in such a way that they precisely coincide at their several points of attachment. It may occur that certain parts have to be fastened to one another at as many as five or six places with the aid of threaded bolt connections. If the high cost involved with accurate attuning, and, consequently, a minimizing of the tolerances, is to be avoided, measures will have to be taken with which deviations can be levelled out. Nowadays, for this purpose case nuts (floating nuts) are used that are located on a plate member that has to be fastened, with their screw hole behind the relatively large hole of that one plate that has to be fastened. In accordance with the dimensions of the slotted hole, said case nuts have a freedom of movement that is limited by retainers welded to that one plate that has to be fastened. Owing to the necessary freedom of position of said case nuts, these will often not be in alignment with the fastening holes of the other part/plate that has to be fastened.
An improved threaded bolt is disclosed in European patent 0.832.363 in the name of assignee. This known threaded bolt provides a solution to many of the above-mentioned problems.
U.S. Pat. No. 5.073.073 discloses a threaded bolt having a smooth distal end comprising a right-circular cylindrical distal portion located offset with respect to the shank central axis and a truncated portion located between said distal portion and the threaded shank.
It is also known to provide a threaded bolt with measurement planes by arranging measurement planes at a recess or an elevation with respect to the actual end planes at both the head end and at the insertion end by means of cold deformation. The presence of several radial planes, situated at different axial distances measured along the centre line of the threaded bolt, however, has a detrimental influence on the recognizability and the clearness of the measurement results. This threaded bolt is described in European patent application 0.459.365, the contents of which should be considered inserted here by reference.
Another proposal is known from U.S. Pat. No. 4.846.001, in which a threaded bolt is shown of which the head is provided with a recess with a measurement plane in it, which by finishing has been made sufficiently smooth/level, in order to be used in ultrasonic measuring. The recess is used for accommodating a piezo-electric sensor. In another embodiment the recess is absent and the sensor is placed at the end plane at the head.
There is still a need, however, for a further improved threaded bolt with which, even under the above circumstances, alignment can be guaranteed, and cross-threading is prevented in addition, and which therefore has a practically maximum capacity to align the central axes of holes and threaded bolt, as well as an improved optimal capacity for correcting oblique positions of insertion of the threaded bolt.
For this purpose, the invention provides a threaded bolt having a distal insertion end and a proximal head-end and a threaded shank extending in between, said shank having a longitudinal axis, wherein the distal insertion end comprises a first distal portion that comprises the outermost distal end of the distal insertion end, said outermost distal end being eccentrically located with respect to the central axis of the shank, the first distal portion defining a circumferentially continuous, smooth, non-threaded surface, in which a second distal portion, in proximal direction, connects to said first distal portion, said second distal portion defining a circumferentially continuous, smooth, non-threaded, right-circular cylindrical surface, which is located centrically with respect to the central axis of the shank, wherein the first distal portion has been provided with surfaces, the generatrix of which has a straight course and is inclined with respect to the longitudinal axis.
Preferably, said surfaces of said first distal portion form part of a conical surface, preferably of a same conical surface.
As a result, the threaded bolt according to the invention, owing to the eccentric location of the -at least partly- frusto-conical (truncated-conical) tip, possesses a great capacity for smooth alignment, without there being a chance that the threaded bolt will be damaged when in an oblique position. The alignment procedure will then not be disturbed by a thread. The capacity for alignment is increased, while, when the threaded bolt is being screwed in, the function of the smooth tip of opposing an oblique position, is smoothly taken over by the cylindrical smooth surfaces that, in proximal direction, lie there behind. As a result, even in cases of large deviations in size, the threads only mesh when the threaded bolt is in an at least substantially perpendicular position to the screw hole, and the robot that tightens the threaded bolt can screw in with the set torque without running the risk of deformation or destruction of the thread. Because of the shape of the distal insertion end, not only is the alignment function enhanced, but the function of correcting oblique positions as well. The transition from the first distal portion to the second distal portion is less abrupt than in the aforementioned known threaded bolt.
Preferably, said generatrix and the shank longitudinal axis include an angle within the range of 30 to 60 degrees, more preferably an angle of about 45 degrees.
Preferably, said conical surface has a central axis extending parallel to said shank longitudinal axis. Preferably, said central axis of said conical surface is spaced from said shank longitudinal axis. Preferably, said central axis is spaced from the cylindrical surface of said second distal portion in a direction perpendicular to said shank longitudinal direction.
In a further development of the threaded bolt of the invention, said conical surfaces form part of a truncated cone, said outermost distal end being formed by an end plane. Preferably, said end plane extends perpendicular to said shank longitudinal axis. Preferably, said end plane is circular.
Preferably, in distal end view the boundary of said end plane coincides at least in one location with the boundary of said cylindrical surface of said second distal portion.
Alternatively, in distal end view the boundary of said end plane may be radially inwardly spaced from the boundary of said cylindrical surface of said second distal portion.
In a further development of the threaded bolt according to the invention said second distal portion has a diameter that is larger than the inner diameter of the groove of the thread on the shank and smaller than the outer diameter of the groove of the thread on the shank. Hereby the anti-cross threading properties are still further improved, due to the precise -but still permitting insertion of the bolt- fitting of the second distal portion in the nut.
Preferably, said outermost distal end is entirely located on one side of the central axis of the shank. This causes the alignment function of the threaded bolt according to the invention to be maximized. This is enhanced even more when the eccentricity of the outermost distal end is equal to at least one fourth of the diameter of the shank.
Preferably, said eccentricity of the outermost distal end is equal to at least one fourth of the diameter of the shank.
Preferably, said first distal portion, at least at one side thereof, has surface areas of which the generatrix coincides with the generatrix of surfaces of the threaded bolt lying in front of them in proximal direction. This guarantees a smooth transition.
Preferably, said second distal portion connects to the thread of the shank in proximal direction.
Preferably, said thread of the shank, in the area near the distal portion, is locally interrupted and in which the shank in the same area has been provided with a recess.
The invention moreover relates to a threaded bolt provided with measurement planes for use in ultrasonic length measurement. After the threaded bolt has been fixed in a connection, such a measurement is performed to determine the length change of the threaded bolt, in order to find out the tension within the threaded bolt in that way.
In this respect, in the above described threaded bolt of the invention a first measurement plane extending perpendicular to said shank longitudinal axis has been formed on said proximal head end, said end plane being formed as a second measurement plane extending parallel to said first measurement plane, said first and said second measurement planes being for use in ultrasonic length measurement for determining the tension in the threaded bolt after it has been placed in a connection.
Preferably, said first and said second measurement planes have a plane parallelism of at least 0.05 mm.
Preferably, said first measurement plane is located concentric with respect to said shank longitudinal axis and said second measurement plane is located eccentric with respect to said shank longitudinal axis.
Preferably, said first measurement plane at the head end is located recessed.
It has been established that even if said second measurement plane is located radially aside of said shank longitudinal axis, useful measurements can be carried out.
It is another object of the invention to provide a threaded bolt, which can easily be manufactured or is manufactured and able to provide reliable measurement results. The invention further provides a method for making such a threaded bolt.
From one aspect the invention to that end provides a threaded bolt having a proximal head end and a distal insertion end, the head end and the insertion end being provided with measurement planes for use in ultrasonic length measurement for determining the tension in the threaded bolt after it has been placed in a connection, in which the measurement plane at the insertion end forms the complete end plane there and which has been arranged on the insertion end without final (or as it is called in the art xe2x80x9csecondxe2x80x9d) processing operation.
Preferably, said measurement planes have a plane parallelism of at least 0,05 mm.
Preferably the measurement plane has been arranged at the insertion end by means of an heading treatment.
Said heading treatment can advantageously be performed during an heading treatment performed in a bolt machine, also known as xe2x80x9cbolt makerxe2x80x9d. In such a bolt machine the heading of the head takes place in one operation. During said heading the measurement planes can be realized at both ends, in which the exact axial distance between both measurement planes can be determined.
Alternatively the heading operation for making the measurement planes may take place during the subsequent shank reduction.
By way of a further alternative instead of by means of heading, the measurement plane at the insertion end can indeed be made in the same bolt machine, but then in a following station, where the point is made. This then takes place by means of a machining treatment.